[Pyobjc-dev] Mixin classes

[Johan R. <joh...@gm...>]

I'm trying to implement the informal NSKeyValueBindingCreation protocol.
I would love to make it a mixin-class so I can reuse the functionality
throughout
my application.

Here's how I planned to do it:

class NSKeyValueBindingCreation:
    def bind_toObject_withKeyPath_options_(self, binding, anObject,
keyPath, options):
        ...
    def observeValueForKeyPath_ofObject_change_context_(self, keyPath, anObject,
                                                         change, context):
        ....

class Foo(NSObject, NSKeyValueBindingCreation):
    ....

The problem is that my Foo class won't recognize the
observiceValueForKeyPath:ofObject:change:context: message.

objc.error: NSInternalInconsistencyException - <Foo: 0x35e430>: An
-observeValueForKeyPath:ofObject:change:context: message was received
but not handled.


If I put it directly in Foo it gets recognized.

Poking through the PyObjC manual I found the following lines:

  Multiple inheritance may be used when subclassing an Objective-C
  class, so long as the Objective-C class is the first base class and there
  is only one Objective-C base class. The Objective-C runtime does not
  support multiple inheritance. These mix-in classes should not contain
  different implementations for Objective-C methods. To achieve this
  behavior, Categories should be used instead.

I interpret those lines as that the snippets above should work.
Am I wrong?

How can I, and how should I use mixin classes?